Eddy current magnetic braking device, vehicle braked wheel and aircraft landing gear equipped with such a wheel

Abstract

Eddy current magnetic braking device (1) comprising two external stators (2.1) flanking a central stator (2.2) and two rotors (3) made of electrically conductive material. Each external stator has a surface facing a surface of one of the rotors and carrying a plurality of permanent magnets (11, 13) having a magnetization vector normal to said surface to emit, via said surface, a first magnetic flux capable of generating eddy currents in the rotors. The central stator comprises electromagnets (21) having a magnetization vector parallel to those of the permanent magnets and connected to a controlled power supply (22) to produce a second magnetic flux either opposing or reinforcing the first magnetic flux. Vehicle wheel, aircraft landing gear, and aircraft incorporating such a device. FIGURE IN ABRIDGED: Fig. 3

Description

Title of the invention: Eddy current magnetic braking device, braked vehicle wheel and aircraft landing gear equipped with such a wheel

[0001] The present invention relates to the field of braking vehicle wheels such as aircraft wheels.

[0002] BACKGROUND OF THE INVENTION

[0003] An aircraft wheel generally comprises a rim connected by a web to a hub mounted for rotation on a wheel support shaft (axle or spindle).

[0004] Friction braking devices are known comprising a stack of braking discs which is housed in a space extending between the rim and the hub and which comprises an alternation of rotor discs linked in rotation with the wheel and stator discs fixed relative to the wheel support. The braking device also comprises hydraulic or electromechanical actuators mounted on an actuator holder and arranged to apply a controlled braking force to the stack of discs so as to brake the rotation of the wheel.

[0005] It has been proposed, in particular in document FR-A-2953196, to equip such braked wheels with an electromagnetic auxiliary brake ensuring energy dissipation by means other than mechanical friction.

[0006] Eddy current magnetic braking devices are also known, used for braking vehicle wheels and more particularly aircraft wheels. Document WO-A-2014 / 029962 describes such a device comprising a rotor mounted opposite an electromagnetic stator.

[0007] Document US-A-20200300310 also describes an eddy current magnetic braking device.

[0008] Generally speaking, the performance of an eddy current magnetic braking device depends on the power of the magnets used and their dimensions. The braking device is therefore relatively heavy and bulky when the maximum braking power required is high. This is the case, for example, for use on aircraft, even though mass and size are severe constraints for this use.

[0009] SUBJECT OF THE INVENTION

[0010] The invention aims in particular to propose an eddy current magnetic braking device which at least partially overcomes the aforementioned drawbacks. Summary of the invention

[0011] For this purpose, according to the invention, a magnetic braking device is provided with eddy current comprising two external stators framing a central stator and two rotors made of electrically conductive material. Each external stator has a surface facing a surface of one of the rotors and carries a plurality of permanent magnets having a magnetization vector normal to said surface to emit via said surface a first magnetic flux capable of generating eddy currents in the rotors. The central stator comprises electromagnets which have a magnetization vector parallel to those of the permanent magnets and which are connected to a controlled power source to produce a second magnetic flux either opposing the first magnetic flux or reinforcing the first magnetic flux.

[0012] This arrangement makes it possible to have a significant magnetic flux produced by the permanent magnets of the external stators for a size and mass smaller than those of electromagnets of comparable power and to modulate this magnetic flux by controlling the power supply of the electromagnets of the central stator which will either reinforce the magnetic flux produced by the permanent magnets or on the contrary attenuate or even cancel it. This arrangement therefore makes it possible to benefit from a significant and modular braking torque while maintaining an acceptable mass and size, particularly for aeronautical applications. This arrangement also allows better thermal management and modulation of the braking torque without resorting, or with limited recourse, to mechanical actuation. The integration of the brake in the wheel is therefore facilitated.

[0013] According to optional characteristics, used individually or in whole or in part in combination: - stators and rotors are disc-shaped and have collinear central axes; - the plurality of magnets comprises first magnets and second magnets arranged alternately, the first magnets producing the first magnetic flux and each of the second magnets having a magnetization vector substantially perpendicular to the magnetization vectors of the first magnets between which it is located; and the magnets have widths such that the first magnets are spaced two by two by a first distance less than a second distance separating the second magnets two by two; - the width of the second magnets is approximately 70% that of the first magnets; - the magnets are arranged in a Halbach pattern.

[0014] The invention also relates to a braked wheel equipped with such a device and an aircraft landing gear equipped with such a wheel.

[0015] Other characteristics and advantages of the invention will emerge on reading the following description of particular and non-limiting embodiments of the invention. Brief description of the drawings

[0016] Reference will be made to the accompanying drawings, among which:

[0017] [Fig-1] [Fig.l] is a partial schematic view of an aircraft equipped with a landing gear according to the invention;

[0018] [Fig.2] [Fig.2] is a partial view of a wheel according to the invention, in axial half-section;

[0019] [Fig.3] [Fig.3] is an enlarged schematic view of a part of the braking device according to the invention integrated in this wheel;

[0020] [Fig.4] [Fig.4] is a perspective view of this braking device;

[0021] [Fig.5] [Fig.5] is a perspective view of the braking device engaged in the wheel according to the invention;

[0022] [Fig.6] [Fig.6] is a perspective view of the stators of the braking device according to the invention;

[0023] [Fig.7] [Fig.7] is a side view of the stators of the braking device according to the invention;

[0024] [Fig.8] [Fig.8] is a representation of the poles of the magnets and electromagnets illustrating two modes of supplying the electromagnets of the braking device according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] With reference to Figures 1 and 2, the braking system according to the invention is carried by an aircraft 100 comprising landing gears 101. Each landing gear 101 comprises a leg having one end provided with two coaxial shafts 102 on each of which a wheel 103 is mounted to pivot. Each wheel 103 comprises, in a manner known per se, a hub 104 mounted to pivot on the shaft 102 and a rim 105 connected to the hub 104 by a web 106.

[0026] According to the invention, the wheels 103 are equipped with a magnetic braking device, generally designated 1, housed in an annular space 107 defined between the hub 104 and the rim 105.

[0027] Also referring to [Fig. 3], the magnetic braking device 1 comprises three fixed elements, namely two external stators 2.1 and a central stator 2.2, and two mobile elements, or rotors 3. The stators 2.1, 2.2 and the rotors 3 are in the form of discs, coaxial with the wheel 103, therefore having collinear central axes.

[0028] More precisely here, the central stator 2.2 is arranged between the external stators 2.1; each rotor 3 is arranged between one of the external stators 2.1 and the central stator 2.2 so that each rotor 3 has main faces, one facing a main face of one of the external stators 2.1 and the other facing one of the main faces of the central stator 2.2. The main faces of each rotor 3 are parallel. to the main faces of the stators 2.1, 2.2 which frame it and are separated from them by an air gap.

[0029] The stators 2.1, 2.2 are connected in rotation to the shaft 102 or to the leg of the landing gear 101, here by means of a torque tube 4, while the rotors 3 are connected in rotation to the wheel 103, here to the rim 105 of the wheel 103 by means of peripheral notches engaged on bars 5 fixed to the rim 105. Thus, each rotor 3 rotates on itself around its central axis relative to the stators 2.1, 2.2 which frame it: during this movement of the rotor 3 in a circumferential direction, the main faces of the rotor 3 remain opposite the main faces of the stators 2.1, 2.2 which frame it and parallel to them.

[0030] The rotors 3 are made of copper or any other electrically conductive material. They are kept spaced apart from each other by central blocks 6c in an arc of a circle, each opposite two external blocks 6e in an arc of a circle extending opposite the external periphery of each rotor 3 between two notches. Each triplet of blocks 6c, 6e is fixed by two bolts 7 extending axially and passing through said blocks 6c, 6e. It is understood that two adjacent triplets of blocks 6c, 6e define between them a notch receiving one of the bars 5. The blocks 6c, 6e are therefore in contact with the bars 5 over their entire length and in this way participate in the evacuation by conduction of the heat produced in the rotors 3 by the circulation of the eddy currents and also ensure the transmission of the torque between the rotors 3 and the rim 105. The blocks 6c, 6e are for example made of carbon which is advantageous for its thermal conductivity and also for its low density..

[0031] Also referring to Figures 6 and 7, each external stator 2.1 comprises a plurality of permanent magnets capable of generating eddy currents in the rotor 3 when the rotor 3 pivots opposite the external stator 2.1. The magnets, here based on rare earths, are for example 24 in number and are preferably fixed on a magnetic steel support, or even on a non-magnetic support.

[0032] The plurality of permanent magnets comprises first magnets 11, 13 having a first magnetization vector substantially perpendicular to the main face of the external stator 2.1 and being separated two by two by a second magnet 12, 14 having a second magnetization vector substantially perpendicular to the first magnetization vectors of the two first magnets 11, 13 between which the second magnet 12, 14 is located. It is recalled that the magnetization vector indicates the direction of the magnetic field generated by a magnet and extends in the magnet from the South pole to the North pole. More precisely, the magnets 11, 12, 13, 14 have the shape of angular sectors and have a length measured in a radial direction of the stator and an average width measured in a locally tangential direction of the disks (i.e. perpendicular to the direction of the length) half of said length. Lengths and widths are measured in directions locally parallel to the facing surfaces (the main faces).

[0033] The magnets 11, 12, 13, 14 are arranged in a Halbach pattern, alternating along the circumferential direction of the stator as follows: a magnet 11, a magnet 12, a magnet 13, a magnet 14, a magnet 11, a magnet 12, a magnet 13, a magnet 14 and so on...

[0034] In this case, for the external stator 2.1 adjacent to the veil 106: - each magnet has its magnetization vector which comes out of the main face of the external stator 2.1 (its North pole opens onto the main face of the external stator 2.1 towards the rotor 3), - each magnet 12 has its magnetization vector which extends from the neighboring magnet 11 towards the neighboring magnet 13, - each magnet 13 has its magnetization vector which enters the main face of the external stator 2.1 (its South pole opens onto the main face of the external stator 2.1 towards the rotor 3), - each magnet 14 has its magnetization vector which extends from the neighboring magnet 11 towards the neighboring magnet 13.

[0035] For the external stator 2.1 opposite the veil 106: - each magnet has its magnetization vector which enters the main face of the external stator 2.1 (its South pole opens onto the main face of the external stator 2.1 towards the rotor 3), - each magnet 12 has its magnetization vector which extends from the neighboring magnet 11 towards the neighboring magnet 13, - each magnet 13 has its magnetization vector which leaves the main face of the external stator 2.1 (its North pole opens onto the main face of the external stator 2.1 towards the rotor 3), - each magnet 14 has its magnetization vector which extends from the neighboring magnet 11 towards the neighboring magnet 13.

[0036] It is understood that the magnets 12, 14 arranged on each side of the same magnet 11 have their magnetization vector oriented in opposite directions.

[0037] Each magnet 11 of one of the two external stators 2.1 faces one of the magnets 11 of the other of the two external stators 2.1 and each magnet 13 of one of the two external stators 2.1 faces one of the magnets 13 of the other of the two external stators 2.1.

[0038] According to an advantageous version of the invention, the magnets 11, 12, 13, 14 have widths such that the first magnets 11, 13 are spaced two by two by a first distance (equal to the width of the second magnets 12, 14) less than a second distance (equal to the width of the first magnets 11, 13) separating the second magnets 12, 14 two by two. The best results are obtained when the width of the second magnets 12, 14 is approximately 70% of that of the first magnets 11, 13.

[0039] The lengths of the magnets 11, 12, 13, 14 are here identical to each other. Alternatively, the lengths of the first magnets 11, 13 are identical to each other and the lengths of the second magnets 12, 14 are identical to each other. The lengths of the first magnets 11, 13 are greater than the lengths of the second magnets 12, 14. Preferably, the length of the second magnets 12, 14 is approximately 70% of those of the first magnets 11, 13.

[0040] It is understood that the magnets 12, 14 occupy a smaller surface area on the main face of each external stator 2.1 than that of the magnets 11, 13.

[0041] The arrangement of the magnets 11, 12, 13, 14 makes it possible to optimize and concentrate the magnetic flux produced by the first magnets 11, 13 by reducing the return path of the magnetic flux which passes through the second magnets 12, 14 and not through their support, the mass of which can be reduced since it does not need to provide a magnetic flux conduction function. This allows an increase in the braking torque provided while limiting the mass and size of the device.

[0042] The central stator 2.2 carries electromagnets 21 each arranged between one of the first magnets 11, 13 of one of the external stators 2.1 and one of the first magnets 11, 13 of the other of the external stators 2.1. There is one electromagnet 21 for each pair of first magnets 11, 13 opposite each other, i.e. twelve electromagnets 21. Each electromagnet 21 is arranged between the two first magnets opposite each other to have a coil having a winding axis parallel to the magnetization vectors of the first magnets 11, 13 in such a way that each electromagnet 21 has its magnetization vector parallel to the magnetization vectors of the first magnets 11, 13. Each coil is connected to a controlled power source 22 making it possible to circulate in said coil an electric current either in a first direction or in a second direction opposite to the first direction so that: - in the first direction, the electromagnet 21 generates a magnetic flux in the same direction as those produced by the first magnets 11, 13 which surround it ( [Fig.8] above); - in the second direction, the electromagnet 21 generates a magnetic flux in a direction opposite to those produced by the first magnets 11, 13 which surround it ([Fig.8] below).

[0043] We understand that: - in the first direction, the magnetic flux produced by the electromagnet 21 reinforces the magnetic fluxes produced by the first magnets 11, 13 which surround it, generating a maximum of eddy currents in each rotor 3 ([Fig.8] at the top); - in the second direction, the magnetic flux produced by the electromagnet 21 attenuates or even cancels the magnetic fluxes produced by the first magnets 11, 13 which surround it so that the eddy currents circulating in the rotors 3 are weaker or even almost nullified ([Fig.8] below).

[0044] The controlled power source 22 can be controlled by the pilot of the aircraft who can modify the direction of the current supplying the coils of the electromagnets 21 but also the intensity of the current supplying the coils of the electromagnets 21. It is therefore possible to modulate the magnetic flux produced by each magnetic triplet formed by each electromagnet 21 and the first magnets 11, 13 opposite it.

[0045] Preferably, each rotor 3 has a thickness such that a skin effect (otherwise called a film effect or Kelvin effect) is generated from each face of the rotor 3 over more than half of the thickness of the rotor 3 at least over a range of possible relative speeds of the rotor 3 with respect to the stators 2.1, 2.2. The eddy currents generated from the two faces will then circulate in the central part of each rotor 3, which will increase the braking torque. This results in a “superposition of the skin effects”, the thickness of the rotor 3 being sufficiently small to obtain this effect while satisfying the thermal and mechanical constraints.

[0046] It is understood that to cause braking, the controlled power source 22 is controlled by the pilot to circulate the current in the coils in the first direction and that, to interrupt braking, the controlled power source 22 is controlled by the pilot to circulate the current in the coils in the second direction. It will be noted that below a certain rotational speed of the rotors 3, the braking torque is negligible regardless of the power supply to the electromagnets 21. It will then possibly be necessary to consider an additional brake also serving as a parking brake.

[0047] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0048] In particular, the device may have a structure different from that described.

[0049] The shape, arrangement and dimensions of the magnets may be different from those described. For example, the magnets 11, 12, 13, 14 all have the same dimensions. Preferably, the first magnets 11, 13 will represent approximately 70% of the surface area of ​​the element that carries them, but this is not mandatory. Similarly, the magnets 11, 12, 13, 14 are arranged in a Halbach pattern, but this is not mandatory.

[0050] The number of rotors and / or the number of stators may be different from those mentioned.

[0051] The device described is axial flow but the invention is applicable to radial flow operation (with tubular drums instead of discs) or radial flow operation. operation combining axial flow and radial flow.

[0052] The blocks 6c, 6e are made of a material capable of allowing the blocks to ensure heat evacuation by conduction, from the rotors 3 to the bars 5, and / or torque transmission between the bars and the rotors. The blocks 6c, 6e may be made of any suitable material and for example of metal such as copper.

[0053] Although each triplet of blocks 6c, 6e is fixed by two bolts 7, it can be fixed by any other means.

[0054] The magnetic braking device according to the invention can be associated with a conventional friction braking device which comprises friction members, for example a stack of carbon discs, and a plurality of electromechanical actuators carried by an actuator holder. Each electromechanical actuator comprises an electric motor and a pusher capable of being moved by the electric motor to press the stack of discs. The electromechanical actuator is thus intended to produce a controlled braking force on the stack of discs. A method of controlling the braking devices is for example known from document FR-A-2953196.

[0055] The invention can be used on any type of vehicle, for example aerial, land or amphibious vehicles, or any industrial or transport mobile equipment requiring braking.

Claims

Claims

1. Eddy current magnetic braking device (1), comprising two external stators (2.1) framing a central stator (2.2) and two rotors (3) made of electrically conductive material, each external stator having a surface facing a surface of one of the rotors and carrying a plurality of permanent magnets (11, 13) having a magnetization vector normal to said surface for emitting via said surface a first magnetic flux capable of generating eddy currents in the rotors, the central stator comprising electromagnets (21) which have a magnetization vector parallel to those of the permanent magnets and which are connected to a controlled power source (22) for producing a second magnetic flux either opposing the first magnetic flux or reinforcing the first magnetic flux.

2. Device according to claim 1, wherein the stators (2.1, 2.2) and the rotors (3) have a disc shape and have collinear central axes.

3. A device according to claim 1, wherein the plurality of magnets comprises first magnets (11, 13) and second magnets (12, 14) arranged alternately, the first magnets (11, 13) producing the first magnetic flux and each of the second magnets (12, 14) having a magnetization vector substantially perpendicular to the magnetization vectors of the first magnets between which it is located; and the magnets (11, 12, 13, 14) have widths such that the first magnets (11, 13) are spaced two by two by a first distance less than a second distance separating the second magnets (12, 14) two by two.

4. A device according to claim 3, wherein the width of the second magnets (12, 14) is approximately 70% that of the first magnets (11, 13).

5. Device according to claim 3 or 4, wherein the magnets (11, 12, 13, 14) are arranged in a Halbach pattern.

6. Braked vehicle wheel (103) comprising a braking device (1) according to any one of the preceding claims, comprising a rim (105), a disc (106) or a hub (104) to which the movable element (3) of the braking device (1) is rotationally connected.

7. Wheel according to claim 6, in which blocks (6c, 6e) are fixed to an external periphery of the rotors (3) to bear against bars (5) integral with the rim (105).

8. Wheel according to claim 7, in which the blocks (6c, 6e) are made of a material capable of allowing the blocks to ensure heat evacuation by conduction, from the rotors (3) to the bars (5), and / or torque transmission between the bars and the rotors.

9. Landing gear (101) comprising a leg having one end carrying a shaft (102) on which is mounted the hub (104) of a wheel (103) according to any one of claims 6 to 8, the stators (2.1, 2.2) of the braking device (1) being rotationally linked to the leg.

10. An aircraft (100) comprising a landing gear (101) according to claim 9.

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